Container for storing food and process and apparatus for making that container

ABSTRACT

Disclosed is a container for storing product, a process and apparatus for making that container, a process and apparatus for drawing and blow forming plastic into a paperboard outer container and a process and apparatus for heat sealing a container. The container comprises a paperboard outer container and a plastic inner container which has been drawn and blow formed into the outer container. At the mouth of the container are horizontal plastic flanges which extend about the periphery of the container at least about 1/8 inch outwardly from the plastic inner container. Vertical flanges extend downwardly at least about 1/8 inch from the horizontal flanges. After product is placed in the container, the container is sealed by a heat sealable cover. A plastic overcap may be provided which engagedly fits around the container at its top.

This is a division of application Ser. No. 28,719, filed Apr. 9, 1979,which was a division of application Ser. No. 745,834, filed Nov. 26,1976, now U.S. Pat. No. 4,155,697.

BACKGROUND OF THE INVENTION

Containers for storing food are well known in the art. It is well knownthat such containers may be produced from many different materials andcombinations of materials, e.g., paperboard, glass, aluminum and certainplastics. There are, of course, advantages and disadvantages whichinhere in the use of each of those different materials. For example,paperboard is a relatively strong container material but suffers fromthe disadvantage that it is relatively permeable to gases and,therefore, foods stored in containers constructed solely from paperboardlose their freshness at a relatively rapid rate. On the other hand,glass, aluminum and some plastic materials are relatively impermeable togases, but to obtain sturdy containers from those materials is expensivebecause of the relatively high cost of those materials.

It is therefore most desirable in the food container art to provide acontainer which is sturdy, relatively impermeable to gases andrelatively inexpensive. The containers of the present invention satisfyeach of those three criteria.

The present invention is also directed to a process and apparatus formaking that sturdy, relatively impermeable and inexpensive container.

SUMMARY OF THE INVENTION

The container of the present invention comprises a paperboard outercontainer and a plastic inner container which has been drawn and blowformed into the paperboard outer container. The outer containercomprises at least one vertical wall. Preferably, the outer containerhas four vertical walls and a bottom and is coated with polyethylene.

The drawn and blow formed plastic inner container with one exceptionconforms in shape and abuts with the outer container. That one exceptionis at the inside bottom edge or edges of the outer container defined bythe intersection of the vertical wall or walls of the outer containerand the bottom of the outer container. At those edges of the outercontainer, the plastic inner container is rounded and spaced about 1/8inch to about 3/8 inch from the inside bottom edge or edges of the outercontainer.

The strength of the containers of the present invention is substantiallyenhanced by spacing the plastic inner container from the inside bottomedge or edges of the paperboard outer container in the above-describedmanner. This advantage is particularly important when the containers areused to store relatively large volumes, e.g. 1 gallon or more, ofrelatively dense food, e.g. mustard or catsup. We have discovered thatif the drawn and blow formed plastic substantially abuts the insidebottom edge or edges of the paperboard outer container, then thatabutting plastic ruptures substantially more readily than if the plasticis spaced from the inside bottom edge or edges.

At the mouth of the container is at least one horizontal plastic flangewhich extends about the periphery of the mouth of the container at leastabout 1/8 inch outwardly from the plastic inner container. At least onevertical flange extends downwardly at least about 1/8 inch from the atleast one horizontal flange. Those flanges must extend outwardly anddownwardly at least about 1/8 inch to give the container adequatestrength and to insure an adequate heat seal between a later describedheat sealable cover and the horizontal flange.

The heat sealable cover referred to above may be precut and scored sothat the cover is heat sealed to substantially the entire surface areaof the horizontal flanges. Additionally, we prefer to provide the heatsealable cover with at least one vertical pull tab which extendsparallel to the at least one vertical flange. That at least one verticalpull tab protects the heat seal from rupture during storage and providesmeans for manually breaking the heat seal when it is so desired.Alternatively, the heat sealable cover may be cut concurrently with theheat sealing operation, again so that substantially the entire surfacearea of the horizontal flange is heat sealed. The heat sealable cover isconstructed from at least paperboard, preferably cartonboard, andsealing material, e.g., wax or heat sealable polymer. Preferably,aluminum foil is also employed in the heat sealable cover to provide acover which is highly impermeable to air and water. The most preferredheat sealable cover comprises a laminate of aluminum foil sandwichedbetween cartonboard and sealing material. The aluminum foil is attachedto the cartonboard by any suitable adhesive. The cartonboard ispreferably at least about 12 point board to give the heat sealable coveradequate strength and rigidity.

The container of the present invention may be provided with an overcapwhich engagedly fits around the container at its top. Preferably, theovercap is constructed from styrene.

The containers of the present invention are constructed by positioning apaperboard outer container having at least one vertical wall into afemale mold. Thereafter, a heated sheet of plastic is drawn into afemale mold with a male mandrel. The male mandrel is provided with holesin communication with a gas supply so that after the plastic is drawninto the mold, the plastic may be blow formed into substantial abutmentwith the inside vertical wall or walls of the paperboard outercontainer. As discussed above, the paperboard outer container may or maynot have a bottom. In the event that the outer container has a bottom,then the plastic is blow formed so that the plastic is spaced from thebottom edge or edges of the outer container in the above describedmanner.

As indicated above, the paperboard outer container of the presentinvention has at least one vertical wall. When the outer container hasone vertical wall, preferably a cross-section of that wall along ahorizontal plane is circular in configuration. When the outer containerhas more than one vertical wall, those vertical walls, of course,intersect one another to form vertical edges.

We have discovered that in order to adequately blow form plastic intopaperboard outer containers having more than one vertical wall requiresa specially designed male mandrel. First, each vertical edge of thecontainer formed by the intersection of two vertical walls must have gasdirected substantially into it. This is accomplished by providing themandrel with rows of substantially aligned air holes directedsubstantially into each edge formed by the intersection of two verticalwalls. We have discovered that even distribution of plastic during blowmolding is obtained if the male mandrel has rows of substantiallyaligned air holes directed as described above.

We have also discovered that a conical mandrel must be employed toobtain adequate plastic distribution when the paperboard outer containerhas more than one vertical wall. The reason for this is that when amandrel with vertical sidewalls is employed, plastic tends to web orgather at the top edges of the container at the intersection of twovertical walls. This "webbing" or "gathering" impedes the formation ofan adequate heat seal between the heat sealable cover and the at leastone horizontal flange of the container, and is therefore to be avoided.

As indicated above, the paperboard outer container of the presentinvention preferably has a bottom. When the paperboard outer containerhas a bottom, that container, of course, has a bottom edge or edgesformed by the intersection of the bottom and the vertical wall or wallsof the paperboard outer container. We have discovered that evendistribution of plastic is obtained during blow forming if the malemandrel has a row of substantially horizontally aligned holes directedsubstantially at the bottom edge or edges formed by the intersection ofthe bottom and vertical wall or walls of the paperboard outer container.

Prior to drawing, the plastic sheet is heated by any suitable means to adrawable state. The male mandrel and female mold are designed andarranged so that the horizontal and vertical flanges discussed above areformed during the end of the drawing operation. Preferably, initiallythe paperboard outer container extends about 1/16 inch above the femalemold. This permits the plastic to be compacted and bonded onto the boardduring the drawing operation so as to obtain a lock between the plasticand paperboard outer container.

After the plastic has been drawn and blow formed as described above,food is placed into the container by any suitable means. Thereafter, thecontainer is sealed with a heat sealable cover. The container is heatsealed by placing a layer of heat sealable cover material between aheated platen and a female mold with the container positioned therein.The heat sealable cover is then heat sealed to the at least onehorizontal flange by pressure and heat applied by a heated platen.

The heated platen of the present invention may be heated by any suitablemeans to a temperature sufficient to heat seal the cover to the at leastone horizontal flange in the above described manner. For an adequateheat seal to be obtained, we have found that air must be evacuated fromthe inside of the container prior to contact of the heat sealable covermaterial to the at least one horizontal flange. The preferred means foraccomplishing this objective is to provide the heated platen with an airdisplacement block. That air displacement block projects from the heatedplaten so that the heat sealable cover material is pushed into theinterior of the container, thereby evacuating air therefrom, before theheat sealable cover material is pressed by the heated platen onto the atleast one horizontal flange.

After the heat sealable cover has been heat sealed to the at least onehorizontal flange of the container, the container may be provided withan overcap which engagedly fits around the container at its top.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded view of a container of the present invention.

FIG. 2 shows a sectional view of the arrangement of the male mandrel,female mold, plastic sheet and paperboard outer container before theplastic sheet is drawn into the paperboard outer container.

FIG. 3 shows a sectional view of the arrangement of the male mandrel,female mold, plastic sheet and paperboard outer container during thedrawing of the plastic sheet into the paperboard outer container.

FIG. 4 shows a sectional view of the arrangement of the male mandrel,female mold, plastic sheet, and paperboard outer container while theplastic sheet is being blow formed in the female mold.

FIG. 5 shows a sectional view of the arrangement of the heated platen,heat sealable cover material, female mold and the paperboard outercontainer with a plastic sheet drawn and blow formed therein prior toheat sealing the heat sealable cover material onto the horizontalflanges of the container.

FIG. 6 is a schematic view of an apparatus for producing the containerof the present invention.

FIG. 7 shows an enlarged cross-sectional view of a heat sealable coverwhich may be used in the present invention.

FIG. 8 shows an enlarged cross-sectional view of another heat sealablecover which may be used according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown an exploded view of a container ofthe present invention. The container comprises a paperboard outercontainer 10. That outer container is preferably constructed from foldedpolyethylene coated paperboard and comprises four vertical walls 11. Asshown in FIGS. 2-5, the outer container preferably also comprises abottom 12.

The container of the present invention also comprises a plastic innercontainer 13 which, as is described more fully below, has been drawn andblow formed into the paperboard outer container 10. The plastic innercontainer 13 comprises four vertical walls 14 and bottom wall 15. Fourhorizontal flanges 16 extend from the plastic inner container about theperiphery of the mouth of the container. Four vertical flanges 17 inturn extend from the four horizontal flanges 16. The horizontal andvertical flanges 16 and 17 extend at least about 1/8 inch from the innercontainer 13 and horizontal flanges 16, respectively. We have discoveredthat both the horizontal and vertical flanges must be imensioned asdescribed above in order for the containers of the present invention tohave adequate strength.

It will be observed upon reference to FIG. 1 that the plastic innercontainer is rounded at the points where vertical walls 14 intersectbottom 15. The reason for this is that the strength of the containers ofthe present invention is substantially enhanced by spacing the plasticinner container from the edges of the paperboard outer container formedby the intersection of vertical walls 11 and bottom 12. Specifically, toenhance the strength of the containers of the present invention, theplastic inner container should be spaced from about 1/8 inch to about3/8 inch and preferably 1/4 inch from the edges formed by theintersection of vertical walls 11 and bottom 12.

We have discovered that when the plastic inner container closely abutsthe edges formed by the intersection of vertical walls 11 and bottom 12,then the plastic in those edges ruptures substantially more readily thanwhen the plastic is spaced from those edges in the above describedmanner. This advantage of the present invention is particularlyimportant when the containers of the present invention are used to store1 gallon or more of readily dense food, e.g. mustard or catsup.

While we do not wish to be bound to any particular theory, we believethat the superior strength of containers with a plastic inner containerwhich is spaced from the bottom edges of a paperboard outer containermay be due to two factors. First, we have discovered that plastic whichis blow formed into close abutment with those bottom edges is thinnerthan plastic which is blow formed to be spaced from the bottom edges inthe above described manner. This thinning out of the plastic isparticularly apparent at the 90° bottom corners defined by theintersection of two side walls and the bottom of the outer container.For this reason we believe it is particularly critical that the plasticinner container be spaced from the outer container at the 90° bottomcorners. Secondly, we believe that the air space between the plasticinner container and bottom edges of the outer container serves as acushion to help absorb shocks which occur when the containers areshipped and handled.

The plastic which is used to form the plastic inner container andflanges of the present invention may be chosen from a plurality ofdifferent materials. Of course, the plastic used must be a thermoplasticmaterial which is capable of being drawn and blow formed into the innercontainer. Another important factor in determining the plastic whichshould be used for the inner container is the food which is to be storedin the container. The reason for this is that some foods are moresusceptible to alteration upon exposure to oxygen or moisture andtherefore desirably are stored in containers constructed from highbarrier plastics. Examples of high barrier plastics which may be used inthe present invention are Barex, a styrene acrylonitrile copolymer, andCycopac, an acrylonitrile-butadiene-styrene terpolymer.

There are, of course, many other plastics which may be used to form theplastic inner container, including medium barrier plastics, e.g.butadiene-styrene copolymer, and low barrier plastics, e.g. polyethyleneor styrene, as well as the high barrier plastics referred to above.

Additionally, the plastic inner container of the present invention maybe formed of a composite of two or more plastic materials which arejoined together, preferably in the absence of adhesive, e.g. Barophane,manufactured by National Can Corporation. For example, the innercontainer may be constructed from a composite of a layer of high densitypolyethylene joined in the absence of adhesive to a layer of Barex orCycopac. We prefer that the composite is drawn and blow formed into thecontainer so that the polyethylene layer faces the interior of thecontainer because heat sealable cover 18 is generally more readily heatsealed onto polyethylene than onto Barex or Cycopac.

As shown in FIG. 1, heat sealable cover 18 is precut and scored so thatthe cover 18 is heat sealed to substantially the entire surface area ofhorizontal flanges 16. Additionally, as shown in FIG. 1, the heatsealable cover is provided with vertical pull tabs 92 which extendparallel to vertical flanges 17. Vertical pull tabs 92 protect the heatseal from rupture during storage and provide means for manually breakingthe heat seal when it is so desired. Preferably vertical pull tabs 92cover at least 80% of the surface area of vertical flanges 17 but itshould be understood that vertical pull tabs 92 are not an essentialelement of the present invention.

Referring now to FIG. 7, there is shown a cross-sectional view of themost preferred heat sealable cover which may be used in the presentinvention. As shown, heat sealable cover comprises a layer ofpaperboard, preferably cartonboard 71, which is attached to a layer ofaluminum foil 72 by a layer of glue 73. A layer of sealing material 74is attached by its own substance to the layer of aluminum foil 72.

Referring now to FIG. 8 there is shown, in cross-section, an alternativeconstruction for heat sealable cover of the present invention. In theconstruction shown in FIG. 8, a layer of aluminum foil 81 is attached bya layer of glue 82 to a layer of cartonboard 83. A layer of sealingmaterial 84 is attached by its own substance to the layer of cartonboard83.

In both embodiments shown in FIGS. 7 and 8, the layer of aluminum foilis present for its barrier properties, i.e. the layer of aluminum foilsretards the flow of gases and moisture through the heat sealable cover.It should be understood that the layer of aluminum foil and the layer ofglue which is required to attach that foil to the cartonboard may beeliminated in the event that high barrier properties are not requiredfor the food which is to be stored in the container.

The cartonboard in the heat sealable cover gives that cover rigidity andstrength. That cartonboard should preferably be at least about 12 pointcartonboard in order to provide the heat seal with enough support sothat the seal will not be broken too easily during storage and transportof the container.

The sealing material in the heat sealable cover may be any wax, hot meltadhesive, or polymer material which can be heat sealed to the plasticflange and stripped therefrom without destroying that flange. Forexample, polyvinylacetate-polyethylene or vinylacetate-ethylene-acrylatepolymers may be used as sealing material. The most preferred sealingmaterial is a material manufactured by Gravure Flex Corporation, SouthHackensack, New Jersey under the Code name F 827 T.

Again referring to FIG. 1, preferably the container of the presentinvention also comprises overcap 19. That overcap is designed so that itengagedly fits around the container at its top. As shown in FIG. 1,overcap 19 desirably has locking lugs 20 which are arranged on theovercap so that the overcap engagedly interlocks with vertical flanges17. Additionally, the side walls 91 of overcap 19 are preferably taperedoutwardly so that the overcaps can be stacked one onto the other.Finally, overlap 19 is preferably provided with recessed antiwarpcircles 90. It is to be understood, however, that the locking lugs,tapered sides, and antiwarp circles are not part of the presentinvention. In the most preferred embodiment, overcap 19 is constructedfrom styrene.

The primary function of overcap 19 is to serve as a cover for thecontainer once the heat seal between the heat sealable cover 18 andhorizontal flanges 16 is broken. A secondary purpose of overcap 19 is toprovide protection for the heat sealable cover 18 during shipping andstorage of the container.

Referring now to FIGS. 2-4, there is shown stepwise the process fordrawing and blow forming plastic inner container 13 into paperboardouter container 10 while simultaneously forming horizontal flanges 16and vertical flanges 17. Specifically, referring to FIG. 2 there isshown a sectional view of the arrangement of male mandrel 21, femalemold 22, plastic sheet 23 and paperboard outer container 10 prior todrawing plastic sheet 23 into paperboard outer container 10.

As shown in FIG. 2, paperboard outer container 10 is placed into femalemold 22 substantially as shown. In the most preferred embodiment,vertical walls 11 of paperboard outer container 10 initially extendoutwardly from the female mold 22. The reason for this is so thatplastic sheet 23 is crushed into the bonded to paperboard outer carton10 during the drawing operation. Preferably, the paperboard outercontainer 10 extends initially from about 1/32 inch to about 3/32 inch,and most preferably about 1/16 inch outwardly from female mold 22. Wehave discovered that when the paperboard outer container 10 extends morethan about 3/32 inch above female mold 22, the paperboard folds orcrumples excessively. On the other hand, if paperboard outer container10 extends less than about 1/32 inch above female mold, then the desiredgood lock between the plastic and paperboard outer container is notobtained.

As shown in FIG. 2, plastic sheet 23 is initially positioned betweenmale mandrel 21 and female mold 22. As shown, plastic sheet 23 is largerthan required for drawing and blow forming plastic inner container 13into the paperboard outer container 10. The reason for this, as will bemore fully explained below, is that in the most preferred embodimentplastic sheet 23 is simultaneously drawn and blow formed into aplurality of paperboard outer containers 10. Additionally, horizontaland vertical flanges 16 and 17 are also simultaneously formed for aplurality of containers in the most preferred embodiment of the presentinvention. It is to be understood, however, that it is within the scopeof the present invention to draw and blow form plastic sheet 23 into asingle paperboard outer container 10.

However, when plastic is simultaneously drawn and blow formedsimultaneously into a plurality of paperboard outer containers, weprefer to use a single plastic sheet 23, portions of which are drawn andblow molded into each paperboard outer container 10. As will bedescribed more fully below, in this preferred embodiment, plastic sheet23 is cut by the coaction of male mandrel 21 and female mold 22 so as toprovide distinct plastic inner containers 13 for each paperboard outercontainer 10.

As is evident from FIGS. 2-4, male mandrel 21 and female mold 22 arearranged and constructed so that male mandrel 21 may engage female mold22. Prior to positioning plastic sheet 23 as shown in FIG. 2 anddescribed above, that plastic sheet is heated to a thermal formabletemperature, i.e. a temperature sufficient to permit drawing and blowforming the plastic sheet 23 into paperboard outer container 10.Additionally, depending on the plastic used, the ambient temperature,and the temperature that the plastic was preheated to, it may benecessary to maintain the plastic at a thermal formable temperatureduring the drawing operation by heating mandrel 21 to an appropriatetemperature by any suitable means.

The thickness of plastic sheet 23 may be varied widely depending on thesize of the container, and the plastic used. For example, with Barexplastic and a one gallon container, it is preferred that plastic sheet23 be between about 15 to 30 mils thick, and most preferably be about 20mils thick.

Referring now to FIG. 3, there is shown in cross-section section thearrangement of male mandrel 21, female mold 22, plastic sheet 23 andpaperboard outer container 10 at one stage during the drawing of theplastic sheet 23 into paperboard outer container. As is apparent fromFIG. 3, as the drawing operation continues past the stage shown in FIG.3, eventually the base 24 of male mandrel 21 contacts plastic sheet 23.

The base 24 of male mandrel 21 comprises protruding vertical flangeforming means 25 which is in alignment with recessed vertical flangeforming means 26 in female mold 22. Preferably, protruding verticalflange forming means 25 has a sharp protruding edge 27 which is alignedwith sharp recessed edge 28 of recessed vertical flange forming means26.

As will be appreciated upon reference to FIGS. 3 and 4, male mandrel 21and female mold 22 are designed and arranged so that when the drawingoperation is completed, protruding vertical flange forming means 25 hasentered and substantially filled recessed vertical flange forming means.A necessary consequence of this is that plastic sheet 23 is cut duringthe drawing operation so as to provide, as discussed above, a distinctplastic inner container 13 and horizontal and vertical flanges 16 and17.

It will also be appreciated upon reference to FIGS. 3 and 4 that malemandrel 21 and female mold 22 are designed and arranged so that theupper edge of paperboard outer container 10, which initially protrudedoutside female mold 22 as discussed above, is crushed or compressed intothe female mold 22 during the drawing operation so that paperboard outercontainer 10 no longer protrudes from female mold 22.

Referring now to FIG. 4, there is shown a sectional view of male mandrel21, female mold 22, paperboard outer container 10, and plastic sheet 23at one stage during the blow forming of plastic sheet 23. As shown inFIG. 4, male mandrel 21 is in communication with a source of air so thatair can be directed out of air holes 29 disposed in male mandrel 21. Itshould be understood that while gases other than air may be employed inthe blow forming step, in the preferred embodiment, air is employed toblow form the plastic.

Because paperboard outer container 10 has bottom 12, there must beprovided means for relieving pressure in the container which otherwisewould build up in the container during the blow forming step of thepresent invention. To accomplish this purpose, we prefer to provide pinholes in the bottom 12 of paperboard outer container 10. For example,for a 1 gallon container with a 5 1/2 inch square bottom, we prefer toprovide six pin holes along each edge of the bottom 12 of the container.Of course, suitable means must also be provided for relieving airpressure from female mold 22.

A wide range of air pressures may be used according to the presentinvention. For example, the air pressure at the air intake to malemandrel may be between about 10 to 50 psig. We prefer, however, forreasons of safety and economics, to use relatively low air pressures,i.e. less than about 35 psig.

As indicated above, the preferred outer containers of the presentinvention have a rectangular cross-section and a bottom. Mostpreferably, the containers of the present invention have a squarecross-section along a plane parallel to the bottom of the container. Wehave discovered that under the above set of conditions a speciallydesigned male mandrel substantially enhances the blow forming process.First, the mandrel should be conical shaped. Second, the mandrel shouldhave four rows of aligned air holes which are arranged and constructedso that air is directed from each row of holes into one of the fouredges of the container defined by the intersection of two of the fourvertical walls 11 of paperboard outer container. Two of those rows ofsubstantially aligned air holes are shown in FIG. 4. Additionally, themale mandrel should have a row of generally horizontally aligned airholes. That row of generally horizontally aligned air holes is arrangedand constructed so that air is directed from each hole into one of thefour edges of the container defined by the intersection of containerbottom 12 and one of the four vertical walls 11.

For best results each of the rows of generally aligned air holes whichare directed into one of the edges defined by intersecting verticalwalls should extend at least 50°% of the length of the conical portionof male mandrel 21 and preferably at least about 70°% of that length.Additionally, the row of generally horizontally aligned air holes shouldextend substantially about the entire circumference of the male mandrel21.

We have discovered that unless a conical male mandrel is used, excessivewebbing or gathering of plastic occurs at the top of the container atthe four edges defined by the intersection of vertical walls 11. Thismay prevent the creation of an adequate heat seal between horizontal andvertical flanges 16 and 17 and heat sealable cover 18.

We have also discovered that each edge of the container defined byeither two intersecting vertical side walls or an intersecting side walland bottom wall should have a set of air holes directed substantially atthat edge as described above or, otherwise, the plastic will be unevenlyblow formed.

It should be understood that a specially designed mandrel may also berequired when other shapes of containers are constructed according tothe present invention. For example, to construct a hexagonal containerwith six side walls and a bottom, a conical male mandrel with six rowsof generally vertically aligned air holes and a row of horizontallyaligned air holes should be employed. Each row of generally verticallyaligned air holes should be arranged and constructed so that air isdirected from that row of holes substantially into one of the six edgesof the container defined by the intersection of the six vertical walls.Additionally, the row of horizontally aligned air holes should bearranged and constructed so that air is directed from each holesubstantially into one of the six edges of the container defined by theintersection of container bottom and one of the six vertical walls.

As with the container with four vertical walls described above, the malemandrel used in the construction of a container with six vertical sidewalls should be conical to prevent excessive webbing or gathering ofplastic at the top of the container at the edges defined by intersectingside walls. We have discovered that in order to prevent such webbing orgathering generally a conical male mandrel should be used if thecontainer has intersecting vertical side walls. Obviously, because acontainer with a circular side wall does not have intersecting verticalside walls, but rather a single continuous side wall, a conical malemandrel is not required to construct such containers.

As with the container with four vertical walls and a bottom walldescribed above, the air holes of the male mandrel used for constructinga container with six vertical side walls should be arranged andconstructed so that air is jetted from each hole into a portion of anedge defined by the intersection of the vertical side walls of theintersection of a vertical wall and bottom wall. We have discovered thatgenerally each edge of a container formed by either the intersection oftwo vertical side walls or a vertical side wall and bottom should have arow of aligned air holes associated with it so that in use air isdirected substantially into each such edge. If the air holes are not soarranged and contructed, we have found that the plastic is unevenly blowformed.

It was indicated above that a wide range of air pressures at the airintake of the male mandrel are contemplated in the present invention.However, of course, the air pressure in the container must be controlledso that plastic inner container is spaced from the bottom edges of thepaperboard outer container defined by the intersection of the bottom ofthe outer container and each vertical wall of that container.Specifically, as described above, the blow forming process is controlledso that the plastic inner container is spaced from about 1/8 inch toabout 3/8 inch from those bottom edges of the outer container.

One advantage of using positive pressure rather than a vacuum in thepresent invention, is that positive pressure can be readily controlledto cause the plastic inner container to be spaced from the bottom edgesof the outer container while a vacuum can not be readily controlled tocause the drawn plastic sheet to expand from male mandrel so that theplastic is spaced from the bottom edges of the outer container. Anotheradvantage of using positive pressure is that the air may be heatedeither by the male mandrel or by external means. While the use of heatedair is not always required, the use of such heated air helps to maintainthe plastic in a thermal formable state during the blow forming step ofthe present invention.

Referring now to FIG. 5, there is shown a sectional view of thearrangement of heated platen 51, heat sealable cover material 52, femalemold 22, and paperboard outer container 10 with a plastic innercontainer 13 drawn and blow formed therein, just prior to heat sealingthe heat seal cover onto horizontal flanges 16. Heat sealable covermaterial is, of course, positioned so that the above described layer ofsealing material in the heat sealable cover material 52 faces the femalemold. Heated platen 51 may be heated by any suitable means to atemperature so that the heat sealable cover material 52 may be heatsealed to horizontal flanges 16 by pressing said cover material ontosaid horizontal flanges with the heated platen 51.

Heated platen 51 is provided with air displacement block 53. During theheat sealing operation, heated platen 51 is brought into contact withheat sealable cover material 52 so that said cover material is pressedonto and heat sealed to horizontal flanges 16. As is apparent from FIG.5, air displacement block 53 contacts the heat sealable cover material52 before the heat sealable cover material is pressed by the platen ontohorizontal flanges 16. We have discovered that by so contacting the heatsealable cover material 52, air is evacuated from the interior of thecontainer prior to the creation of the heat seal between heat sealablecover material 52 and horizontal flanges 16. If the interior of thecontainer of the present invention is not evacuated by suitable means,e.g. by an air displacement block, we have discovered that an adequateheat seal is not obtained.

As shown in FIG. 5, heat sealable cover material 52 is larger thanrequired to provide a heat sealable cover for container 10. The reasonfor this, as will be more fully explained below, is that in theembodiment shown in FIGS. 5 and 6, a plurality of heat sealable coversare simultaneously cut and heat sealed onto a plurality of containers.

When a pluarlity of heat sealable covers are simultaneously cut and heatsealed, we prefer to use a single piece of heat sealable cover material52, portions of which are used to form each heat sealable cover. As willbe appreiciated upon reference to FIG. 5, heated platen is provided withprotruding vertical pull tab forming means 54. As shown, the protrudingvertical pull tab forming means 54 has a sharp protruding edge 55. Asshown in FIG. 5, heated platen 51 and female mold 22 are arranged andconstructed so that when heated platen contacts heat sealable covermaterial 52 and presses and heat seals that material onto horizontalflange 16, it also presses and folds that material onto vertical flange17. Additionally, the heated platen 51 and female mold are arranged andconstructed so that while the heated platen presses heat sealable covermaterial onto horizontal and vertical flanges 16 and 17, sharpprotruding edge 55 cuts heat sealable cover material 52 so as to providea distinct heat sealable cover for each container.

In the embodiment shown in FIG. 5 there is provided heat sealable cover,including vertical pull tabs, which extend parallel to substantially theentire surface area of vertical flanges 17. However, as indicated abovein connection with the description of FIG. 1, it is within the scope ofthe present invention to provide a heat sealable cover which does notinclude vertical pull tabs. As also indicated above, and as shown inFIG. 1, the heat sealable cover 18 may be precut rather than cut duringthe heat sealing operation. When a precut heat sealable cover isemployed, that cover may be appropriately cut, as is shown in FIG. 1,preferably so that a substantial portion, e.g. at least about 80%, ofthe surface area of the vertical flanges 17 are covered by the verticalpull tabs.

After the containers of the present invention are provided with a heatsealable cover 18, the containers may be provided with overcap 19 by anysuitale means. For example, overcap 19 may be snapped onto the containerby hand.

Referring now to FIG. 6, there is shown a schematic view of an apparatuswhich may be used for producing the container of the present invention.A plurality of folder paperboard outer containers 10 may be fed to aplurality of female molds 22 by any suitable means, e.g. chute means 61or by hand. Plastic sheet 23 is positioned with respect to male mandrel21 and female mold 22, as described above in connection with thedescription of FIG. 2, by any appropriate means. As shown in FIG. 6,plastic sheet is rolled from roll means 62 into the required position.Thereafter, the plastic is drawn, blow formed, and cut as describedabove in connection with the description of FIGS. 2-4 at mandrel station63. Prior to reaching mandrel station 63, plastic sheet is heated to athermal formable state at heating station 69. Food may then beintroduced into the container by any suitable means 64 or by hand.

Heat sealable cover material 52 is then positioned with respect toheated platen 51 and female mold 22 as described above in connectionwith FIG. 5. As shown in FIG. 6, heat sealable cover material is rolledfrom roll means 65 into the required position. With heat sealablematerial so positioned, the containers of the present invention are heatsealed at heat sealing station 66.

After the heat sealing step the containers of the present invention areremoved from the female mold and preferably provided with overcap 19 bysuitable means or by hand.

As shown in FIG. 6, each paperboard outer container is moved from oneprocess station to another process station in a single female mold 22.Female mold 22 may be moved form one station to another by anyappropriate means, e.g. conveyor means or the like.

It is to be understood that while the invention has been described abovewith respect to preferred embodiments, variations and equivalentsthereof may be perceived by those skilled in the art. For example, itshould be understood that the containers of the present invention do notrequire an overcap. Additionally, the containers of the presentinvention may be used to store products other than food, e.g.pharmaceuticals, cosmetics, or industrial chemicals.

The container shown in FIG. 1 has continuous paperboard vertical sidewalls. However, it is to be understood that the vertical side walls ofthe paperboard container may have cutouts so that the material stored inthe containers may be viewed through a "window" in at least one verticalwall of the container.

Finally, the containers described above have heat sealable coversconstructed from paperboard and sealing material and preferablypaperboard, sealing material and aluminum foil. However, it is to beunderstood that the heat sealable covers of the present invention may becontructed from any material which may be heat sealed to the horizontalflanges of the present invention and stripped therefrom withoutdestroying those flanges. For example, heat sealable cover may beconstructed from plastic, e.g. Barex, a styrene acrylonitrile polymer.

What is claimed is:
 1. An apparatus for drawing and blow forming plasticinto a paperboard outer container and for heat sealing that containercomprising:(a) a female mold comprising at least one vertical wall and abottom wall, said female mold adapted to recieve a paperboard outercontainer; (b) a male mandrel provided with holes in communication witha source of gas whereby gas may be directed from the interior of saidmandrel into said female mold; (c) means for positioning a sheet ofplastic between said female mold and said male mandrel; (d) means forheating the sheet of plastic positioned between said female mold andsaid male mandrel in subpart (c) above; (e) means for positioning themale mandrel with respect to the female mold so that said male mandrelmay engage said female mold, said male mandrel and female mold beingconstructed so that when so positioned with respect to one another and asheet of plastic is positioned between said male mandrel and femalemold, the sheet of plastic may be drawn by said male mandrel into apaperboard outer container positioned in said female mold and,thereafter, the sheet of drawn plastic may be blow formed in thepaperboard outer container positioned in said female mold, said malemandrel and female mold being further provided with means for forming atleast one horizontal flange connected to and extending outwardly atleast about 1/8 inch from the drawn and blow formed plastic and at leastone vertical flange connected to and extending downwardly at least about1/8 inch from said at least horizontal flange to obtain a containercomprising a paperboard outer container, a plastic inner container, atleast one horizontal flange and at least one vertical flange; (f) meansfor introducing product into the container described in subpart (e)above; (g) a platen, said platen comprising a heating means and an airdisplacement block non-movable with respect to the remainder of theplaten and projecting downwardly from the platen; (h) means forpositioning a sheet of heat sealable cover material between said femalemold and said platen when said female mold and said platen arepositioned so that they may engage each other; and (i) means forpositioning said platen with respect to the female mold so that saidplaten may engage said female mold, said platen and female mold arrangedand constructed so that (i) when container of the type described insubpart (e) above is positioned in the female mold and a sheet of heatsealable cover material is positioned between said platen and the femalemold and the female mold and platen are moved into engagement with eachother, the heat sealable cover material may be pressed and heat sealedonto the at least one horizontal flange of the container, and (ii)before the sheet of heat sealable cover material is pressed onto atleast one horizontal flange, the ari displacement block of the platencontacts the sheet of heat sealable cover material to push the heatsealable cover material into the interior of the container and toevacuate air from the interior of the container.
 2. The apparatus ofclaim 1 wherein:(a) the female mold comprises at least three verticalwalls; (b) the male mandrel is conical and is provided with at leastthree rows of substantially aligned holes, each row of substantiallyaligned holes arranged and constructed so that gas may be directed intoan edge of the female mold defined by the intersection of two verticalwalls of the female mold.
 3. The apparatus of claim 1 wherein the malemandrel comprises a row of substantially horizontally aligned holesarranged about the circumference of the male mandrel, said row ofsubstantially horizontally aligned holes arranged and constructed sothat gas may be directed substantially into an edge of the female molddefined by the intersection of the bottom and at least one vertical wallof the female mold.
 4. The apparatus of claim 2 wherein the male mandrelcomprises a row of substantially horizontally aligned holes arrangedabout the circumference of the male mandrel, said row of substantiallyhorizontally aligned holes arranged and constructed so that gas may bedirected substantially into the edges of the female mold defined by theintersections of the bottom and at least three vertical walls of thefemale mold.
 5. An apparatus for heat sealing a container comprising:(a)a female mold, said female mold comprising at least one vertical walland a bottom wall and adapted to receive a container comprising apaperboard outer container having at least one vertical wall, a plasticinner container, at least one horizontal flange connected to andextending outwardly at least about 1/8 inch from said plastic innercontainer, and at least one vertical flange connected to and extendingdownwardly at least about 1/8 inch from said at least one horizontalflange; (b) a platen, said platen comprising a heating means and an airdisplacement block non-movable with respect to the remainder of theplaten and projecting downwardly from the platen toward the bottom ofthe female mold said platen and female mold arranged and constructed sothat (i) when a container of the typedescribed in subpart (a) above ispositioned in the female mold and a sheet of heat sealable covermaterial is positioned between said platen and the female mold and thefemale mold and platen are moved into engagement with each other, theheat sealable cover material may be pressed and heat sealed onto the atleast one horizontal flange of the container, and (ii) before the sheetof heat sealable cover material is pressed onto the at least onehorizontal flange, the air displacement block contacts the sheet of heatsealable cover material to push the sheet of heat sealable covermaterial into the interior of the container and to evacuate air from theinterior of the container.
 6. The apparatus of claim 5 wherein theplaten further includes means for pressing and folding said heatsealable cover material onto said at least one vertical flange of thecontainer.
 7. The apparatus of claim 5 wherein said platen and femalemold include means for coacting to cut said heat sealable cover materialafter it is pressed onto said at least one horizontal flange of thecontainer.